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		<title>three.js PMREM directional light test</title>
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				<a href="https://threejs.org" target="_blank" rel="noopener">three.js</a> -
				PMREM test by <a href="https://github.com/elalish" target="_blank" rel="noopener">Emmett Lalish</a>
				<br>
				<br>1: white metal. 2: white dielectric. 3: black dielectric.
				<br>PMREM on: HDR with a single bright pixel. PMREM off: DirectionalLight.
				<br>The difference between these renders indicates the error in the PMREM approximations.
			</div>
		</div>

		<script type="importmap">
			{
				"imports": {
					"three": "../build/three.module.js",
					"three/addons/": "./jsm/"
				}
			}
		</script>

		<script type="module">

			import * as THREE from 'three';

			import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
			import { RGBELoader } from 'three/addons/loaders/RGBELoader.js';

			import { GUI } from 'three/addons/libs/lil-gui.module.min.js';

			let scene, camera, controls, renderer;

			function init() {

				const width = window.innerWidth;
				const height = window.innerHeight;
				const aspect = width / height;

				// renderer

				renderer = new THREE.WebGLRenderer( { antialias: true } );
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( width, height );

				// tonemapping
				renderer.toneMapping = THREE.ACESFilmicToneMapping;
				renderer.toneMappingExposure = 1;

				document.body.appendChild( renderer.domElement );

				window.addEventListener( 'resize', onWindowResize );

				// scene

				scene = new THREE.Scene();

				// camera

				camera = new THREE.PerspectiveCamera( 40, aspect, 1, 30 );
				updateCamera();
				camera.position.set( 0, 0, 16 );

				// controls

				controls = new OrbitControls( camera, renderer.domElement );
				controls.addEventListener( 'change', render ); // use if there is no animation loop
				controls.minDistance = 4;
				controls.maxDistance = 20;

				// light

				const directionalLight = new THREE.DirectionalLight( 0xffffff, 0 ); // set intensity to 0 to start
				const x = 597;
				const y = 213;
				const theta = ( x + 0.5 ) * Math.PI / 512;
				const phi = ( y + 0.5 ) * Math.PI / 512;

				directionalLight.position.setFromSphericalCoords( 100, - phi, Math.PI / 2 - theta );

				scene.add( directionalLight );
				// scene.add( new THREE.DirectionalLightHelper( directionalLight ) );

				// The spot1Lux HDR environment map is expressed in nits (lux / sr). The directional light has units of lux,
				// so to match a 1 lux light, we set a single pixel with a value equal to 1 divided by the solid
				// angle of the pixel in steradians. This image is 1024 x 512,
				// so the value is 1 / ( sin( phi ) * ( pi / 512 ) ^ 2 ) = 27,490 nits.

				const gui = new GUI();
				gui.add( { enabled: true }, 'enabled' )
					.name( 'PMREM' )
					.onChange( value => {

						directionalLight.intensity = value ? 0 : 1;

						scene.traverse( function ( child ) {

							if ( child.isMesh ) {

								child.material.envMapIntensity = 1 - directionalLight.intensity;

							}

						} );

						render();

					} );

			}

			function createObjects() {

				let radianceMap = null;
				new RGBELoader()
					// .setDataType( THREE.FloatType )
					.setPath( 'textures/equirectangular/' )
					.load( 'spot1Lux.hdr', function ( texture ) {

						radianceMap = pmremGenerator.fromEquirectangular( texture ).texture;
						pmremGenerator.dispose();

						scene.background = radianceMap;

						const geometry = new THREE.SphereGeometry( 0.4, 32, 32 );

						for ( let x = 0; x <= 10; x ++ ) {

							for ( let y = 0; y <= 2; y ++ ) {

								const material = new THREE.MeshPhysicalMaterial( {
									roughness: x / 10,
									metalness: y < 1 ? 1 : 0,
									color: y < 2 ? 0xffffff : 0x000000,
									envMap: radianceMap,
									envMapIntensity: 1
								} );

								const mesh = new THREE.Mesh( geometry, material );
								mesh.position.x = x - 5;
								mesh.position.y = 1 - y;
								scene.add( mesh );

							}

						}

						render();

					} );

				const pmremGenerator = new THREE.PMREMGenerator( renderer );
				pmremGenerator.compileEquirectangularShader();

			}

			function onWindowResize() {

				const width = window.innerWidth;
				const height = window.innerHeight;

				camera.aspect = width / height;
				updateCamera();

				renderer.setSize( width, height );

				render();

			}

			function updateCamera() {

				const horizontalFoV = 40;
				const verticalFoV = 2 * Math.atan( Math.tan( horizontalFoV / 2 * Math.PI / 180 ) / camera.aspect ) * 180 / Math.PI;
				camera.fov = verticalFoV;
				camera.updateProjectionMatrix();

			}

			function render() {

				renderer.render( scene, camera );

			}

			Promise.resolve()
				.then( init )
				.then( createObjects )
				.then( render );

		</script>
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